Conventionally, when a hub unit is manufactured by assembling a shaft, an inner ring, balls and an outer ring, it is necessary to measure the sizes of the each part in order to cope with variations in the measurement accuracy of the shaft, variations in the measurement accuracy of the inner ring, variations in the measurement accuracy of the outer ring, variations in the size of the balls within specifications thereof, changes in the inner ring raceway size due to press fitting of the inner ring to the shaft, dimensional changes depending on the temperature of each of the shaft, inner ring, balls and outer ring and so on. So, a great deal of time is necessary for the measurements and there is obstructive in shortening the production time of the hub unit and reducing the manufacturing cost.    Patent Document 1: JP H02-159536 A